From "AOL Auto Questions"

.. They usually give a couple of reasons, but in many cases the main
> > reason is extra profit or just habit.
>
> I've noticed the auto manufacturers are in that same extra profit and
> habit mode as well on every new one pumped out.
>
> All I can say Ed, is never do yours. Most people come into a shop with
> the pad backing plate, if not a piston ground into at least one of the
> rotors, wondering what is that funny noise and the vibration in the
> brake pedal?

I am not a professional or even a particularly good DIY mechanic (just
for the record). I think most shops resurface rotors to avoid 'come
back' problems with noise etc. on brake jobs.

On my own cars, I never turn the rotors unless there is a specific
need. I know the 'theory' is to make the flat surfaces of the pad/
rotor match, and to take off any rust or other problems with the
rotor. But even if a rotor is not perfectly flat after a bit of
driving the pads will mate to the rotor and if there were no noise
problems with the old pads there shouldn't be any with the new. Any
time you cut a rotor you are, of course, taking off metal - why do
that if it isn't necessary? Its not just a 'cost' issue.

I also agree with the poster who noted that not all shops use the
brake lathe that well - in fact, I think proper turning of rotors may
very well be a dying art. In the hands of a skilled operator, a rotor
can literally be brought back to life 'from the dead' - but like so
many other things you don't just slap the rotor on the machine and
take a cut.

My opinion, FWIW.

"Ph@Boy" > wrote in message
...
> C. E. White wrote:
>> "Ph@Boy" > wrote in message
>> ...
>>
>>> I could go on, but I'm sure others will have many other reasons as
>>> well.
>>>
>>> Resurfacing rotors is a good thing.
>>
>> I beg to differ. I can't speak for Toyota, but I know Ford and GM
>> specifically says resurfacing is not required when replacing pads
>> unless the rotor is damaged. And then only minor damage can be
>> cleaned up. Significant groving requires rotor replacement.
>> Futhermore, Ford only recommend resurfacing rotors on the car.
>> Unless the brake lathe is in great condition, the chances of it
>> making things worse are significant. Unless the car already has
>> warped or otherwise damaged rotors, I see no reason to routinely
>> turn brake rotors. I know most independent shops routinely turn
>> brake rotors. They usually give a couple of reasons, but in many
>> cases the main reason is extra profit or just habit.
>
> I've noticed the auto manufacturers are in that same extra profit
> and habit mode as well on every new one pumped out.
>
> All I can say Ed, is never do yours. Most people come into a shop
> with the pad backing plate, if not a piston ground into at least one
> of the rotors, wondering what is that funny noise and the vibration
> in the brake pedal?

It has been years since I let a set of pads wear so thin they damaged
a rotor. And back then I was a college student. I slapped on a set of
pads, and never looked back. I had zero problems with the brakes
despite the "groves" in the rotor. GM even says they aren't a problem
unless they are so deep the bottom is below the minimum rotor
thickness. The one time I let a shop cut my rotors it was a disaster.
I took the car with brakes in good condition. They warned me the
brakes were thin, so I let them do a brake job. When I got the car
back the brakes squealed and pulsed like hell. When I complained, they
said the rotors were no good and tried to sell me knew ones. When I
pointed out the brakes were fine when I dropped the car off, they just
walked away. A lot yelling followed. So did new rotors.

>> See:
>> http://www.encyclopedia.com/doc/1G1-92137449.html
>> http://www.aa1car.com/library/2003/bf110322.htm
>> http://www.stoptech.com/tech_info/wp...rakedisk.shtml
>>
>>> OBTW, the biggest factors for hydroplaning are speed of the
>>> vehicle and tire pressure. Tread and water depth make little if
>>> any difference.
>>
>> Oh boy.......you really need to clarify this. See
>> http://www.nhtsa.dot.gov/cars/rules/...8/part5.6.html .
>> You statement is misleading at best. Speed is a major factor for
>> sure. But tread depth is not the trival factor that you impy in
>> your statement. Tire inflation pressure is a major factor once
>> "water depth exceeds the capability of the tread design to remove
>> water." So for minimal depth of water and good condition tread,
>> tire inflation pressure is not a bigger factor that depth of water
>> and tread. Furthermore the formula used is pretty lame since it
>> does not account for sidewall stiffness. Try applying the formula
>> to a run flat tire with all the pressure released and get back to
>> me.
>>
>> See also:
>>
>> http://www.tirerack.com/tires/tirete...e.jsp?techid=3
>>
>>
>> Ed
>>
>>
> 8.7 times the square root of the tire pressure is the formula to
> calculate hydroplane speed in general. It's pretty reliable unless
> you need to go into some physics calculations.

8.7 is the NASA number for airplanes. NHTSA uses 10.35 and they make
it clear this only has validity once "the water depth exceeds the
capability of the tread design to remove water." The ability of tires
to "remove water" varies depending on the original tread design, the
tread depth, and the depth of the standing water. The hydroplaning
formula may work pretty good for heavily worn ties and relatively deep
standing water, but it clearly is just an approximation and can't be
blindly applies. Once again, do the calculation for run flat tires
with the pressure removed. Blindly using the formula implies the car
would hydroplane at 0 mph. I have a number of cars that have
recommended tire pressure of 30 psi or so. Using your preferred
formula (8.7 times the square root of the tire pressure) implies a
hydroplaning speed of 48 mile per hour. I've driven many miles in the
rain at speeds much greater than 48 mph and never hydroplaned. Using
the NHTSA formula gives a more realistic speed of 57 mph, but I've
also exceeded that many times. To be honest, I am not talking about
driving on roads with several inches of water, more like driving
through puddles with 1/4 inch of water. And with tires that still have
significant tread.

> Tire tread depths vary greatly. Most folks don't buy specialty
> tires.

Yes they do. And your point would be?

Ed

C. E. White wrote:
>
> "Ph@Boy" > wrote in message
> ...
>> C. E. White wrote:
>>> "Ph@Boy" > wrote in message
>>> ...
>>>
>>>> I could go on, but I'm sure others will have many other reasons as
>>>> well.
>>>>
>>>> Resurfacing rotors is a good thing.
>>>
>>> I beg to differ. I can't speak for Toyota, but I know Ford and GM
>>> specifically says resurfacing is not required when replacing pads
>>> unless the rotor is damaged. And then only minor damage can be
>>> cleaned up. Significant groving requires rotor replacement.
>>> Futhermore, Ford only recommend resurfacing rotors on the car.
>>> Unless the brake lathe is in great condition, the chances of it
>>> making things worse are significant. Unless the car already has
>>> warped or otherwise damaged rotors, I see no reason to routinely
>>> turn brake rotors. I know most independent shops routinely turn
>>> brake rotors. They usually give a couple of reasons, but in many
>>> cases the main reason is extra profit or just habit.
>>
>> I've noticed the auto manufacturers are in that same extra profit
>> and habit mode as well on every new one pumped out.
>>
>> All I can say Ed, is never do yours. Most people come into a shop
>> with the pad backing plate, if not a piston ground into at least one
>> of the rotors, wondering what is that funny noise and the vibration
>> in the brake pedal?
>
> It has been years since I let a set of pads wear so thin they damaged
> a rotor. And back then I was a college student. I slapped on a set of
> pads, and never looked back. I had zero problems with the brakes
> despite the "groves" in the rotor. GM even says they aren't a problem
> unless they are so deep the bottom is below the minimum rotor
> thickness. The one time I let a shop cut my rotors it was a disaster.
> I took the car with brakes in good condition. They warned me the
> brakes were thin, so I let them do a brake job. When I got the car
> back the brakes squealed and pulsed like hell. When I complained, they
> said the rotors were no good and tried to sell me knew ones. When I
> pointed out the brakes were fine when I dropped the car off, they just
> walked away. A lot yelling followed. So did new rotors.
>
>>> See:
>>> http://www.encyclopedia.com/doc/1G1-92137449.html
>>> http://www.aa1car.com/library/2003/bf110322.htm
>>> http://www.stoptech.com/tech_info/wp...rakedisk.shtml
>>>
>>>> OBTW, the biggest factors for hydroplaning are speed of the
>>>> vehicle and tire pressure. Tread and water depth make little if
>>>> any difference.
>>>
>>> Oh boy.......you really need to clarify this. See
>>> http://www.nhtsa.dot.gov/cars/rules/...8/part5.6.html
>>> .
>>> You statement is misleading at best. Speed is a major factor for
>>> sure. But tread depth is not the trival factor that you impy in
>>> your statement. Tire inflation pressure is a major factor once
>>> "water depth exceeds the capability of the tread design to remove
>>> water." So for minimal depth of water and good condition tread,
>>> tire inflation pressure is not a bigger factor that depth of water
>>> and tread. Furthermore the formula used is pretty lame since it
>>> does not account for sidewall stiffness. Try applying the formula
>>> to a run flat tire with all the pressure released and get back to
>>> me.
>>>
>>> See also:
>>>
>>> http://www.tirerack.com/tires/tirete...e.jsp?techid=3
>>>
>>>
>>> Ed
>>>
>>>
>> 8.7 times the square root of the tire pressure is the formula to
>> calculate hydroplane speed in general. It's pretty reliable unless
>> you need to go into some physics calculations.
>
> 8.7 is the NASA number for airplanes. NHTSA uses 10.35 and they make
> it clear this only has validity once "the water depth exceeds the
> capability of the tread design to remove water." The ability of tires
> to "remove water" varies depending on the original tread design, the
> tread depth, and the depth of the standing water. The hydroplaning
> formula may work pretty good for heavily worn ties and relatively deep
> standing water, but it clearly is just an approximation and can't be
> blindly applies. Once again, do the calculation for run flat tires
> with the pressure removed. Blindly using the formula implies the car
> would hydroplane at 0 mph. I have a number of cars that have
> recommended tire pressure of 30 psi or so. Using your preferred
> formula (8.7 times the square root of the tire pressure) implies a
> hydroplaning speed of 48 mile per hour. I've driven many miles in the
> rain at speeds much greater than 48 mph and never hydroplaned. Using
> the NHTSA formula gives a more realistic speed of 57 mph, but I've
> also exceeded that many times. To be honest, I am not talking about
> driving on roads with several inches of water, more like driving
> through puddles with 1/4 inch of water. And with tires that still have
> significant tread.
>
>> Tire tread depths vary greatly. Most folks don't buy specialty
>> tires.
>
> Yes they do. And your point would be?
>
> Ed
>
I guess you'll be the guy doing the mental calculations as you drive.

wrote:
> . They usually give a couple of reasons, but in many cases the main
>>> reason is extra profit or just habit.
>> I've noticed the auto manufacturers are in that same extra profit and
>> habit mode as well on every new one pumped out.
>>
>> All I can say Ed, is never do yours. Most people come into a shop with
>> the pad backing plate, if not a piston ground into at least one of the
>> rotors, wondering what is that funny noise and the vibration in the
>> brake pedal?
>
> I am not a professional or even a particularly good DIY mechanic (just
> for the record). I think most shops resurface rotors to avoid 'come
> back' problems with noise etc. on brake jobs.

Not to mention the $$$ involved (which buys us nothing in most cases). I
started replacing brake pads in the 70's on my 1970 VW, 1969 Porsche,
1988 Acura & 2003 Accord - never turned a rotor, never replaced a rotor
and never had a problem.

As always, YMMV.

"Ph@Boy" > wrote in message
...

> I guess you'll be the guy doing the mental calculations as you
> drive.

No, I'll be the guy slowing down when he approaches standing water of
unknown depth. I'll also be the guy with decent tread on his tires.

Ed

C. E. White wrote:
>
> "Ph@Boy" > wrote in message
> ...
>
>> I guess you'll be the guy doing the mental calculations as you drive.
>
> No, I'll be the guy slowing down when he approaches standing water of
> unknown depth. I'll also be the guy with decent tread on his tires.
>
> Ed
Fantastic!

Ph@Boy wrote:
> C. E. White wrote:
>>
>> "Ph@Boy" > wrote in message
>> ...
>>
>>> I guess you'll be the guy doing the mental calculations as you drive.
>>
>> No, I'll be the guy slowing down when he approaches standing water of
>> unknown depth. I'll also be the guy with decent tread on his tires.
>>
>> Ed
> Fantastic!

weak.

jim beam wrote:
> Ph@Boy wrote:
>> C. E. White wrote:
>>>
>>> "Ph@Boy" > wrote in message
>>> ...
>>>
>>>> I guess you'll be the guy doing the mental calculations as you drive.
>>>
>>> No, I'll be the guy slowing down when he approaches standing water of
>>> unknown depth. I'll also be the guy with decent tread on his tires.
>>>
>>> Ed
>> Fantastic!
>
> weak.
Ok, hows this.

REALLY FANTASTIC!!!!!!!!

Ph@Boy wrote:
> jim beam wrote:
>> Ph@Boy wrote:
>>> C. E. White wrote:
>>>>
>>>> "Ph@Boy" > wrote in message
>>>> ...
>>>>
>>>>> I guess you'll be the guy doing the mental calculations as you drive.
>>>>
>>>> No, I'll be the guy slowing down when he approaches standing water
>>>> of unknown depth. I'll also be the guy with decent tread on his tires.
>>>>
>>>> Ed
>>> Fantastic!
>>
>> weak.
> Ok, hows this.
>
> REALLY FANTASTIC!!!!!!!!

dude, there's a lot of experienced smart people hang out here. that
means great learning opportunities - if you think about it. much better
to ask questions than b.s.

jim beam wrote:
> Ph@Boy wrote:
>> jim beam wrote:
>>> Ph@Boy wrote:
>>>> C. E. White wrote:
>>>>>
>>>>> "Ph@Boy" > wrote in message
>>>>> ...
>>>>>
>>>>>> I guess you'll be the guy doing the mental calculations as you drive.
>>>>>
>>>>> No, I'll be the guy slowing down when he approaches standing water
>>>>> of unknown depth. I'll also be the guy with decent tread on his tires.
>>>>>
>>>>> Ed
>>>> Fantastic!
>>>
>>> weak.
>> Ok, hows this.
>>
>> REALLY FANTASTIC!!!!!!!!
>
> dude, there's a lot of experienced smart people hang out here. that
> means great learning opportunities - if you think about it. much better
> to ask questions than b.s.
>
You have obviously excluded yourself from your aforementioned group.
Dude. Learn it.